Meeting Abstract

Proprioception, the sense of movement and position of one’s body elements in space, is critical to the motor performance of many animals. Proprioception has been documented in the pectoral fins of fishes; however, pectoral fin morphology, mechanics, and kinematics vary markedly among species and it is unknown whether afferent physiology is adapted to a fin’s biomechanics. In the morphologically diverse clade of wrasses (Labridae), some species use their broad flexible fins for drag-based propulsion, while others employ stiffer fins for lift-based propulsion. Here we compare the proprioceptive afferent response to fin ray bending in a pair of closely related wrasse, the flexible finned Halichoeres bivittatus and the stiff finned Gomphosus varius in order to determine if fin ray afferent physiology can be tuned to fin biomechanics. In both species, phasic afferent activity was observed in response to sinusoidal stimuli between 3 and 6Hz, which corresponds to the range of fin beat frequencies observed in these species. In response to step-and-hold stimuli, a burst of spikes occurred both when the fin was raised from and when it was returned to its resting position. The duration and number of spikes of these bursts increased with increasing bending amplitude. Comparing between species we found that it required a four times larger bending amplitude to elicit afferent activity in H. bivittatus than in G. varius. The spike rate over the hold period (3.5s) also increased with increasing bending amplitude, but again, a larger bending amplitude was required to elicit sustained activity during the hold period in H. bivittatus. The results of this study suggest that sensory physiology can be tuned to the fin mechanics through adapting sensitivity of the proprioceptive system.